This invention generally relates to systems for deploying mechanisms from the hulls of water vehicles, and is specifically concerned with a system for deploying a secondary propulsor unit from the hull of a submarine.
Systems for deploying propulsor units from the hulls of water vessels such as submarines are known in the prior art. However, before the structure and operation of such systems can be fully appreciated, some understanding of the structure and purpose of secondary propulsor systems in such submarines is necessary.
Most submarines include both a primary and a secondary propulsor unit. In nuclear submarines, the primary propulsor unit consists of a screw propeller driven by a shaft which is in turn powered by a nuclear reactor. In the event that the primary propulsor unit should fail, one or more secondary propulsor units are provided. Each secondary propulsor unit generally consists of a submersible electric motor connected to a screw propeller by way of a shaft. During the normal operation of the submarine, the primary propulsor unit drives the submarine, and the secondary propulsor units are withdrawn through an opening in the submarine hull that leads to a storage chamber which protects the propulsor units from mechanical shock and prevents them from creating unnecessary drag forces as the submarine moves. However, if the primary propulsor unit should fail, it becomes necessary to deploy such secondary propulsor units from the storage chamber and through the opening in the hull to a position outside of the hull where their electric motors may be actuated in order to drive the submarine into a port for repairs.
The prior art systems used to deploy such propulsor units have generally comprised an extendible mast which connects the propulsor unit to the ceiling of the storage chamber, and one or more lead screw assemblies for extending and retracting the propulsor unit from the storage chamber to a position outside the hull of the submarine.
While such prior art deployment systems are capable of performing their assigned task, the applicants have noted a number of areas where the design of such systems which could stand improvement. For example, the extendible masts used in such systems are quite heavy, weighing in the neighborhood of several thousand pounds. This weight, in combination with the space requirements for such a mast (which are still considerable even when the mast is collapsed to its most compact condition) disadvantageously reduces the cargo capacity of the submarine that might be better used for carrying food and water supplies, or additional weapons. The same weight and space requirements further necessitates the placement of such prior art deployment systems near the rear of the main drive shaft exit in the aft pressure bulkhead, which is well behind the center of gravity of the sub. Such placement tends to pull the center of gravity of the submarine backwards, thereby necessitating the placement of additional weight in the front of the submarine, which again has the effect of reducing the cargo capacity of the vehicle. Finally, whenever the propulsor unit is deployed by such prior art systems, its storage cavity in the submarine hull is left open, creating fluid drag which not only slows the submarine down, but which also creates unwanted noise that makes it easier for hostile nations to detect the location of the submarine. Additional unwanted drag and noise is created by the hole cover plate (which is mounted on the bottom of the propulsion unit) when the secondary propulsor is deployed into the ambient water and operated.
Clearly, what is needed is a deployment system for such a secondary propulsor unit that is lighter in weight, and smaller in volume than prior art deployment systems which would not only have the effect of increasing the effective cargo capacity of the submarine, but which would also allow the secondary propulsor unit to be mounted closer to the center of gravity of the submarine, thereby increasing its efficiency. Ideally, such an improved deployment system would be simpler in design, but more reliable than existing deployment systems that utilize the combination of a telescoping mast and a plurality of motorized, coordinated lead screws to extend and retract the propulsor unit from the hull of the submarine. Finally, there should be no fluid drag associated with the opening in the hull that leads to the propulsor unit storage chamber when the unit is deployed and operated.